Automated fiber placement machines are widely used to manufacture parts, components and structures from composite material. The materials used in automated fiber placement are typically composed of longitudinal fibers and resin consolidated into tapes, or thin strips, commonly known as “tows.” Individual tapes or tows are manipulated by the fiber placement machine to form a band of material that is deposited onto a tool. Parts are built up layer-by-layer, with tapes or tows of composite material, with the angle at which each layer “ply” is laid onto the tool being precisely determined by the fiber placement machine.
Automated fiber placement enables the construction of complex composite structures having steered or curvilinear fiber paths. This method of producing composite structures is more cost effective than manual methods. It provides an improved structural efficiency due to its ability to orient the fibers along local internal loads paths, which potentially results in lighter structures and lower costs than in structures made by other production methods.
The tows of material used in automated fiber placement are typically wound onto spools. Because the tows include a resin, a backing film, made of paper or another suitable material, is typically applied to the tow as it is wound onto the spool to keep adjacent windings of the tow from sticking to one another.
As the fiber tows are unwound from the spools, during the fiber placement process, the backing paper must be separated from the tow, and be stored, or otherwise disposed of. In prior fiber placement machines, the backing paper has typically been pulled away from the tow utilizing a vacuum system, and is often fed to a chopper or shredding apparatus for storage and removal to a disposal site.
The prior method of removing and disposing of backing paper is undesirable in several respects. Containment of the chopped or shredded backing paper may be difficult, particularly during change out of containers used for storage of the chopped or shredded material. This can lead to the chopped and shredded material escaping from the storage containers, and creating undesirable clutter around the fiber placement machine. Where the backing material is a plastic or other polymer, rather than paper, the individual chopped pieces often have considerable electro-static properties and will stick to surfaces where they alight, making it very difficult to clean up any escaped material.
It is also sometimes necessary, during the fiber placement process, to move the fiber placement head of the fiber placement machine away from the part, and back toward the spools supplying the tows of material, in a manner which necessitates rewinding a substantial length of the tows of material back onto the spools. Where the backing paper has been destroyed, by chopping or shredding, it is no longer available for rewinding onto the spool between layers of the rewound tows, creating the potential for having the rewound tows stick to one another.
It is desirable, therefore, to provide an improved apparatus and method for dealing with the backing paper in an automated fiber placement process in a manner which eliminates one or more of the problems described above.